Changes in physicochemical properties at different development stages of Hexachlamys edulis fruit, an underutilized South American species.

The aim of this work was to study the evolution of fruit size and weight together with the soluble solid and total titratable acidity contents during development of Hexachlamys edulis fruit. Also, the patterns of accumulation of chlorophylls, carotenoids, phenols and antioxidant activity were analysed to define the optimal time for harvesting to obtain maximum nutraceutical characteristics. Fruits were harvested from H. edulis plants growing at the experimental field of the University of Morón (Moreno, Buenos Aires, 34°35'4.98″ SL, 58°48'52.09″ WL, 14 m.a.s.l.). Fresh fruit weight was significantly higher in Medium ripe, Ripe and Overripe fruits (40.1, 39.6 and 38.5 g, respectively) than in Unripe fruits (19.5 g). Soluble solids/total titratable acidity was significantly higher in Overripe fruits (7.3) than in Unripe, Medium ripe and Ripe fruits (3.7-4.5). Total polyphenols were maximum in Unripe fruits (905.8 mg tannic acid/100 g fresh fruit weight) decreasing during the fruit development (426.2-130.4 mg tannic acid/100 g fresh fruit weight). Also, DPPH radical scavenging activity was significantly higher in Unripe fruits (75.7%) compared with Medium ripe, Ripe and Overripe fruits (64.1-17.0%). Positive and significant correlations were observed between total polyphenol content and DPPH radical scavenging activity at each extract concentration (r = 0.74, 0.87, 0.74 and 0.60 for 1.25; 2.50; 5.00 and 12.50 mg/mL, respectively). Total carotenoid content increased during fruit development while at the same time decreased chlorophyll content. Chlorophyll b is the main chlorophyll found. Chromatographic analysis showed that lutein is the main carotenoid found in H. edulis fruits, followed by ß-cryptoxanthin and ß-carotene. As shown by the chromatograms at 280 nm, the concentration of biophenols and the complexity of the biophenol profile decreases during fruit development. Levels of polyphenols and pigments together with the antioxidant activity allow us to consider H. edulis fruit as a functional food.

Neochloris oleoabundans grown in enriched natural seawater for biodiesel feedstock: evaluation of its growth and biochemical composition.

The freshwater microalga Neochloris oleoabundans was used to study algal lipid production in enriched natural seawater, in order to assess its suitability as biodiesel feedstock. Optimal and nitrogen-stress (N-stress) conditions were analyzed. Under optimal conditions, the strain's growth rate was 0.73 div day(-1) and the biomass concentration was 1.5 g L(-1), while it had a maximum lipid yield under N-stress conditions (lipid content: 26% of dry weigh and lipid productivity: 56 mg L(-1) day(-1)). Lipid accumulation was mainly due to a significant increase of triacylglycerol content. Neutral lipids were characterized by a dominance of monounsaturated fatty acids and displayed a fatty acid profile that is suitable for biodiesel. This work offers an interesting alternative for sustainable microalgal oil synthesis for biodiesel production without using freshwater resources. However, further studies are necessary in order to optimize the lipid productivities required for commercial biodiesel production.

Lipid analysis in Haematococcuspluvialis to assess its potential use as a biodiesel feedstock.

The lipid content and composition of Haematococcuspluvialis exposed to stress conditions were analyzed to assess the potential of this microalga as a biodiesel feedstock. The total lipid content of control cells was 15.61% dw, whereas that of cells exposed to continuous high light intensity with nitrogen-sufficient medium (A-stress condition) or under continuous high light intensity with nitrogen-deprivation medium (B-stress condition) was 34.85% dw and 32.99% dw, respectively. The fatty acid profile was similar under all conditions and indicated that the main components were palmitic, stearic, oleic, linoleic, linolenic and linolelaidic acids. The neutral lipid fraction increased about 2-fold under both stress conditions. The percentage of saturated fatty acids in the neutral lipid fraction was 30.36% and 29.62% in cultures grown under A-stress and B-stress, respectively, and 27.81% under control conditions. The monounsaturated fatty acid content was not significantly different in control and A-stress cultures (20.07% and 19.91%, respectively), but was 18.96% under B-stress. The content of polyunsaturated fatty acids was 47.23% under B-stress and 43.15% under A-stress. Growth-rate was higher under A-stress compared to B-stress. This is the first study of H.pluvialis that provides a detailed characterization of its lipid content in relation to bioenergy. The results indicate the potential of this microalga as a biodiesel feedstock; however, culture conditions still have to be improved in order to achieve an adequate energy balance in mass culture.